GC and osteoporosis: Cavalier et al. (2014) compared 25(OH)D analyses across various immunoassays and concluded that these methods are not comparable, especially when levels of vitamin D binding protein are altered, such as during pregnancy, hemodialysis, and osteoporosis in humans. Notably, we did not differentiate between the D2 and D3 forms, leaving it unclear whether the seasonal effects are indicative of UVB action on plant material (D2 formation) or on animals (vitamin D3 formation).